OXYDATION, is a term employed by the later
chemists to express the process by which bodies are
converted into oxyds; and it is allowed on all hands
to be exactly similar to combustion. The nature of
this process has been much disputed; and the question
on this subject involves in itself great part of the con-
troversy between the followers of the immortal Stahl
and the justly celebrated Lavoisier, the founders of
the phlogistic and antiphlogistic theories, which have
for some years divided the chemical world. A view
of this question, sufficiently distinct, may be taken
from the case of metals and their oxyds. Metallic
calces (oxyds say the phlogistians) are simple bodies,
which, when united with phlogiston, form metals.
The process of reduction consists in exposing the ores
of metals to an intense heat in contact with some
inflammable body, most commonly charcoal. Dur-
ing this operation, say they, the charcoal being in-
flamed, parts with its phlogiston, which is immediately
absorbed by the calx, and a metal is formed. La-
voisier and his followers, on the contrary, contend that
metals are simple bodies; but that in the state of
oxyds, that is, as they commonly exist in their ores,
they are combined with oxygen. But as oxygen at
a high temperature is more strongly attracted by char-
coal than by most metals, during the process of re-
duction the oxyd is decomposed, and the oxygen
unites with the charcoal to form carbonic acid, leaving
the regulus or metal free. On this point hinges the
great question, the decision of which must materially
affect almost every part of chemical theory. With-
out presuming to decide between these two opinions,
the former of which is still supported by one or two
chemists of the first rank, we agree with Dr Black
in thinking that, though there still remain a few facts
which have not been thoroughly explained on anti-
phlogistic principles, this theory is much more simple,
and better supported by facts, than any that preceded
it. It has this great advantage over the doctrine of
Stahl, that it requires not the supposition of an ar-
bitrary body, which does not affect our senses, and
of the existence of which we have not even a shadow of
proof. Perhaps we may farther venture to assert, that
though it may be extremely difficult, or even impos-
sible, to refute the phlogistic theory, influenced as we
have all been by a strong prejudice in its favour; yet
had it been brought forward for the first time, when
our knowledge had arrived at the point which it now
holds it never would have been generally received.
See CALCINATION, CHEMISTRY, COMBUSTION, IN-
FLAMMATION.